yamaha atv problem

[ozyboy]

I have a yamaha 250 beartracker atv. It starts and idles fine but when you rev it up it backfires and misses like its running rich. I have put a new plug in and cleaned the carby but it is still the same . It has the vac operated slide which appears ok and the diaphram is ok. air filter is clean. Could it be a ignition module . plug is black when you pull it out. That makes me think it is still in the carby , Has anyone had a problem like this and could you help me out ? thanks :ermm:

[zeppelin]

try adjusting your air screw. if you need more help, look in my jetting thread in the new how to section.

[ozyboy]

It was actually the ignition -cdi module. while the engine was running I held the module and it got really hot so I tapped it against the frame- after unbolting it- and the engine reved up propperly, so I carfully cut the plastic from the module and I could see sparks as some of the diodes inside were arking out. One new module and the problem was fixed. Hope this can help someone else out . Thanks .